An analysis related to various kinds of soil cutting by earth auger,this paper puts forward that running speed of frill should be faster than critical speed so as to increase the efficiency of drill.

• 通过分析长螺旋钻机在切削各类土质时，钻具的角速度与土块运动机理关系，提出确定钻具临界的方法，而工程施工中钻杆的实际转速应大于临界转速，以提高钻机的工作效率。